# wcscpy, wcscpy_s

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< c‎ | string‎ | wide

Defined in header ``<wchar.h>`` |  |
| (1) |
wchar_t* wcscpy( wchar_t* dest, const wchar_t* src ); |  | (since C95) (until C99)
wchar_t* wcscpy( wchar_t* restrict dest, const wchar_t* restrict src ); |  | (since C99)
errno_t wcscpy_s( wchar_t* restrict dest, rsize_t destsz, const wchar_t* restrict src ); | (2) | (since C11)

1) Copies the wide string pointed to by src (including the terminating null wide character) to wide character array pointed to by dest. The behavior is undefined if the dest array is not large enough. The behavior is undefined if the strings overlap.
2) Same as (1), except that it may clobber the rest of the destination array with unspecified values and that the following errors are detected at runtime and call the currently installed constraint handler function:

  - src or dest is a null pointer
  - destsz is zero or greater than RSIZE_MAX / sizeof(wchar_t)
  - destsz is less or equal wcsnlen_s(src, destsz), in other words, truncation would occur
  - overlap would occur between the source and the destination strings
  As with all bounds-checked functions, `wcscpy_s` is only guaranteed to be available if __STDC_LIB_EXT1__ is defined by the implementation and if the user defines __STDC_WANT_LIB_EXT1__ to the integer constant 1 before including `<wchar.h>`.

### Parameters

dest | - | pointer to the wide character array to copy to
src | - | pointer to the null-terminated wide string to copy from
destsz | - | maximum number of characters to write, typically the size of the destination buffer

### Return value

1) returns a copy of dest
2) returns zero on success, returns non-zero on error. Also, on error, writes L'\0' to dest[0] (unless dest is a null pointer or destsz is zero or greater than RMAX_SIZE / sizeof(wchar_t)).

### Example

Run this code

    #include <locale.h>
    #include <stdio.h>
    #include <wchar.h>

    int main(void)
    {
        wchar_t* src = L"犬 means dog";
    //  src[0] = L'狗' ; // this would be undefined behavior
        wchar_t dst[wcslen(src) + 1]; // +1 for the null terminator
        wcscpy(dst, src);
        dst[0] = L'狗'; // OK

        setlocale(LC_ALL, "en_US.utf8");
        printf("src = %ls\ndst = %ls\n", src, dst);
    }

Output:

    src = 犬 means dog
    dst = 狗 means dog

### References

- C23 standard (ISO/IEC 9899:2024):

  - 7.29.4.1.2 The wcscpy function (p: TBD)

  - K.3.9.2.1.1 The wcscpy_s function (p: TBD)

- C17 standard (ISO/IEC 9899:2018):

  - 7.29.4.1.2 The wcscpy function (p: TBD)

  - K.3.9.2.1.1 The wcscpy_s function (p: TBD)

- C11 standard (ISO/IEC 9899:2011):

  - 7.29.4.1.2 The wcscpy function (p: 430)

  - K.3.9.2.1.1 The wcscpy_s function (p: 639)

- C99 standard (ISO/IEC 9899:1999):

  - 7.24.4.1.2 The wcscpy function (p: 376)

### See also

wcsncpywcsncpy_s (C95)(C11) | copies a certain amount of wide characters from one string to another (function)
wmemcpywmemcpy_s (C95)(C11) | copies a certain amount of wide characters between two non-overlapping arrays (function)
strcpystrcpy_s (C11) | copies one string to another (function)
C++ documentation for wcscpy

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